The present invention relates to a method of processing peat and the material produced therefrom. More particularly, it relates to a processing technique for producing inexpensive peat-based pellets having ion exchange and activated carbon-like characteristics for use in contaminated water treatment.
Over the past several decades, the public awareness and concern regarding environmental issues has intensified greatly. To this end, a variety of local, state and federal pollution control agencies have been established to monitor the environment and enforce environmental regulations on individuals, businesses and municipalities. The broad scope of activities encompassed by these agencies illustrates the importance society has placed on controlling potential environmental hazards, including automobile emissions, landfills, industrial emissions, etc.
One extremely important environmental concern is contaminated or waste water. Contaminated water is generated by many different sources. Regardless of the source, the contaminated water must be processed or xe2x80x9cdecontaminatedxe2x80x9d before allowed to flow into a natural water source, such as a pond, wetland, marsh, stream or river. For example, with industrial applications, waste water generated by a particular manufacturing plant must, according to state and/or federal regulations, be treated to remove, or at least minimize, toxic or otherwise harmful substances prior to the waste water being distributed into a city sewer system. Similarly, a city or town""s sewage treatment facility must treat or decontaminate sewage. An additional, although sometimes overlooked, source of potentially toxic waste water is storm runoff. More particularly, as rain water drains from yards and driveways to the xe2x80x9cstorm waterxe2x80x9d sewer system, it accumulates a number of materials including grass clippings, fertilizer, pesticides, oil, metals, etc. Left untreated, these metallic and/or organic contaminants are allowed to flow through the storm sewer system to a nearby retention pond, where they can then contaminate the ground water supply and/or promote uncontrolled growth of bacteria or algae, etc., or directly into lakes, streams or rivers where similar problems can occur.
A number of different waste water treatment methodologies have been developed in recent years. Invariably, the particular technique employed at any one location relates to the type of contaminants otherwise present in the waste water produced by that location. One typical approach for treating contaminated waste water is to direct the waste water through a filtering system. In theory, the filtering system allows relatively xe2x80x9ccleanxe2x80x9d water to flow through while preventing or stopping movement of the contaminant(s). For example, where the waste water contains rocks, paper or other relatively large objects, the filtering system may include a screening. The screening xe2x80x9ccatchesxe2x80x9d the rocks, paper and other material, while allowing water to flow through. The contaminant material is later physically removed from the screen. Where, however, the contaminants in question are much smaller and/or dissolved into the waste water, more sophisticated filtering techniques must be utilized.
The general goal behind alternative filtering techniques is to cycle the contaminated water through a filtering medium for which the particular contaminant(s) in question have an affinity. With this configuration, the contaminants attach themselves to the filtering medium, such that xe2x80x9ccleanxe2x80x9d water exits the system. One example is treatment of aqueous solution (such as water) containing cationic metal contaminants. Treatment of a toxic cationic bearing aqueous solution is normally accomplished through the use of a system incorporating an ion exchange resin or medium. Generally speaking, the ion exchange medium acts to adsorb toxic metal cations and/or other toxic cations. In other words, the toxic cations have an affinity for the ion exchange material, which acts to retain or remove the toxic material from the water or other aqueous solution. The ion exchange medium removes the toxic metal cations and replaces them with a more neutral material, such as sodium, oxygen or potassium.
A wide variety of materials are available for use as an ion exchange material. For example, research has been done on the effectiveness of processed peat. Peat is the product of the partial decay of saturated dead vegetation, and is relatively inexpensive. In order for peat to be useful as an ion exchange material, it normally must be sulfonated. This result is typically achieved by treating the peat with a strong sulfonating agent such as sulfuric acid. One example of such a process is described in U.S. Pat. No. 5,314,638 in which peat is first milled into particles less than 1 millimeter in diameter, then hydrolyzed, debituminized, and thereafter sulfonated. While the method described in U.S. Pat. No. 5,314,638 produces a sulfonated peat material with an improved ion exchange capability, the processing itself is quite expensive and produces only a small quantity of material during each processing cycle. Notwithstanding these potential deficiencies, sulfonated peat is undoubtedly useful as an ion exchange material.
Other common types of contaminants include organic materials, such as hydrocarbons, as well as phosphorous. Activated carbon has been found to be an effective medium for removal of organic materials and phosphorous. While activated carbon can successfully remove undesirable materials from waste water, activated carbon is quite expensive and requires processing to be useful as a filtering medium.
A variety of other specialized filtration mediums are available for treating contaminated water or other aqueous solutions. While these mediums may be highly effective in addressing certain treatment needs, they typically are quite expensive. Along these lines, there does not currently appear to be an inexpensive, integral medium capable of adsorbing toxic cations, organic materials, and phosphorous. Notably, the above-described rain water runoff is but one example of an aqueous solution containing toxic cations, undesirable organic material, and phosphorous.
Pollution control, and in particular treatment of contaminated water, continues to be an extremely important environmental concern. While various ion exchange and organic filtering materials are independently available to facilitate removal of toxic cations or organic contaminants from waste water or other aqueous solutions, the costs associated with these materials are prohibitive. Therefore, a substantial need exists for an inexpensive, natural sorbent for the removal of toxic and harmful metals, organic materials, and phosphorous from wastewater.
The present invention provides an improved method of processing peat for use as an ion exchange and organic sorbent material in the treatment of contaminated water. The method includes sulfonating a supply of raw peat, such as by mixing the raw peat with heated sulfuric acid, to produce sulfonated peat. The sulfonated peat is then combined with a binder medium, resulting in an aggregate material. The aggregate material is then extruded into a plurality of pellets. Each of the plurality of pellets are then baked in an oven maintained at a temperature in the range 800-1200 degree F. (427-649 degree C.); more preferably in the range of approximately 900-1100 degree F. (480-593 degree C.). In one preferred embodiment, the above-describe pellet baking occurs in a low oxygen environment, preferably less than 2% oxygen
The above-described process results in a peat-based product having ion exchange and activated carbon-like characteristics. The pellets are able to remove toxic cations, certain organics, and other materials including phosphorous from contaminated water. For example, the peat-based pellets can be used to filter cationic metals, organic materials, and phosphorous from rain water entering a storm sewer system. Notably, in alternative embodiments, the processing method can be augmented, such as by combining an additional supply of raw peat with the binder medium to improve subsequent extrusion.